There is a technology in which non-jetting of a nozzle is detected by determining the shading which the ink droplets jet at a light receiving element, on a light path comprising a light emitting element and a light receiving element (for example Official Gazette of Japanese Patent Tokkai H10-119307).
In the technology describe in the Official Gazette of Japanese Patent Tokkai H10-119307, in the case where the number of nozzles on the head is increased, in detection of the ink droplets jetted from the nozzle positioned away from the light receiving element, output amplitude is reduced due to light diffraction, and detection is difficult due to S/N deterioration. In order to solve these problems, two sets of light emitting elements and light receiving elements are provided and placed such that the directions of radiation of the detection beam from the light emitting elements are opposite to each other, and detection accuracy is maintained by receiving such that the nozzles of the respective ink jet heads are divided in a front half and a rear half.
Meanwhile, in recent years, there has been demand for development of technology which realizes a method which is simple and low in cost, for detecting non-jetting nozzles in a plurality of nozzle lines such as in line heads.
However, there is absolutely no disclosure of non-jetting detection for a plurality of nozzle lines in the Official Gazette of Japanese Patent Tokkai H10-119307.
In the case where there are multiple nozzle lines such as in a line head, providing multiple light paths and performing detection in the lines can be considered. In this case, in order to perform detection of non-jetting nozzles, each nozzle line is independently detected and a jetting control structure is necessary.
A CPU is often used for jetting control of each nozzle line and for detection of non-jetting nozzles, and in some cases multiple CPUs are needed and this has the disadvantage of increased cost.
In addition, forming each nozzle line based on formation of the voltage waveform which is applied to the head causes the circuits in the jetting control circuit section to be complex and increases the circuit scale and jetting control is therefore difficult.
Furthermore, because the detectors are arranged in lines, detection time is made faster only not in the area of the detector, and this is a problem in that it causes circuits in the jetting circuit control section to be increased.
The problem in this invention is to provide an ink droplet detecting device in which parallel detection can be performed at low cost, and the time for detecting non-jetting can be significantly reduced.